For the IBC in prior art, a cover is generally provided at the port of the valve mounting channel used to install a valve at the bottom of the container. The cover can achieve the effect of dust-proof to some extent. However, some of the known cover can not cover the port completely, resulting poor dust-proof. Further, after the cover at the channel port is flipped, the cover is not connected to any other elements, thus the operator needs to hold the cover while operating it, which is very inconvenient. After the installation of the valve, the operator needs to put the cover back to the channel port manually, which reduces the operation efficiency. Moreover, after the channel port is opened, it occupies extra space of the IBC. Thus, if a forklift is used, the cover is easy to be damaged.
In addition, covers in prior art used to cover the port of the valve mounting channel generally have no thief-evident feature since the cover can be opened directly. Some of the covers employ disposable plastic lids as their thief-evident features. Such plastic lid comprises three parts connected to each other through walls with unequal thicknesses, wherein the middle part is a tearable part, each of the other two parts at two sides has a snap snapping at the valve mounting channel port. The operator tears up the middle part of the plastic cover at first, and then disengages the snap from the valve mounting channel port at both sides when opening the cover, which is very inconvenient. Moreover, a general tool can be used to disengage the snap of the plastic lid at both sides. The middle part will not be damaged or torn, and the intact cover will be removed due to the plasticity of the plastic itself, resulting poor thief-evident effect. At the same time, the cover can not be reused, thereby increasing the cost. In addition, the fitting part located at the valve mounting channel port may be damaged while tearing the plastic lid.